Wow, so much judgement about women ageing on this thread!
Women going grey can decide to live with it, go blonde, dye dark and spend a lot of time and money having frequent top ups, or home dye dark and get blocky colour that often has a gingery tone.
None of those will disguise the fact you are going grey. None of them will make you younger than you are. Pure white or silver can look stunning, but the in between stage can look quite mousy on some women. So some women choose to go blonde.
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You are literally, in your OP emoji, sneering at your friend's choices.
You're in your 40s - the next 20 years will see some friends choosing to cut their hair short because it is literally the only thing that works for some women's thinning hair. Some will start wearing cardigans because it's the only thing that works for some menopausal women. Some will have to give up eye make or contact lenses because their eyes will no longer tolerate them. Some will find that thinning lips or hooded eyes have a massive impact on how they look. Some will be in flowing bright coloured garments because they have put on weight or in frumpy comfortable shoes because their feet won't fit in anything stylish any more.
And some people will sneer at their middle aged mumsy choices but actually absolutely none of that matters. Because by the time you get to your 60s, you'll also have lost friends far too young to cancer, you will know people so depressed they have given up caring what they look like, and you will realise that just enjoying looking the best you can on a daily basis is a statement of resilience and optimism that should be applauded and not sneered at.